From the Super Mario Wiki
Retrieved from "https://www.mariowiki.com/index.php?title=Gunslinger&oldid=2704088"
The object is to tap all the 8-bit cans so they land in the slots on the left, earning the player 300, 800 or 5,000 points respectively. Once this is done, 3D barrels fly in. The barrels have to be tapped repeatedly to destroy them so they release classic Nintendo items, like a Super Scope or R.O.B..